1. Field of the Invention
The present invention relates to an antenna of a portable electronic device such as cellular phone, notebook computer or personal digital assistant, and more particularly to an antenna used for receiving digital television signals.
2. Description of Related Art
There are many antennas used for receiving digital television signals such as the ones disclosed in U.S. Pat. No. 6,819,297, U.S. Pat. No. 6,639,555, U.S. Pat. No. 6,259,416, Taiwan Patent No. I255,589, I240,451 and M285,154, and Taiwan Patent Publication No. 521,455.
Among these, Taiwan Patent Publication No. 521,455 discloses a miniaturized planar antenna of digital television, it comprises a base plate whose upper and lower surfaces respectively are a strip line formed by copper foil printing and a plurality of parallel rampart-line-typed antennas formed by copper foil printing and respectively disposed on the upper and the lower surfaces of the base plate, intersected and connected to the strip line and distributed in two symmetrical quadrants, in which each quadrant has at least three sets of antennas.
Accompanying the development of the combination of a digital television and a portable electronic product such as a cellular telephone, notebook computer or PDA, miniaturizing a broadband antenna of the digital television is an unavoidable tendency.
Please refer to FIG. 1. For miniaturizing an antenna 10, it is general to combine a first surface of a circuit board 11 with a metal radiator 12; the metal radiator 12 is a meander line so as to attain the requirement of the size miniaturization. Furthermore, a grounding terminal 13 is combined to a second surface of the circuit board 11; the grounding terminal 13 generally is a metal film. One end of the radiator 12 is connected to a micro-strip line 14 and one end of the micro-strip line 14 is used as a feeding point 141.
The antenna 10 mentioned above can attain to the requirement of the miniaturization, but the bandwidth thereof is rather narrow such that the electromagnetic signal transmission efficiency is rather bad.